A guide to the Tx of cellulitis and other soft-tissue infections
Diagnostic and therapeutic priorities vary for the 8 types of infection reviewed.
PRACTICE RECOMMENDATIONS
› Start trimethoprim-sulfamethoxazole, clindamycin, doxycycline, minocycline, or a third- or fourth-generation fluoroquinolone for patients with cellulitis likely caused by community acquired methicillin-resistant Staphylococcus aureus (MRSA). A
› Consider culturing for MRSA and treating with oral doxycycline or trimethoprim-sulfamethoxazole for resistant cases of folliculitis. C
› Perform complete surgical debridement promptly if necrotizing fasciitis is suspected. C
› Prescribe broad-spectrum antibiotics for necrotizing fasciitis, covering both anaerobes and aerobes including MRSA. C
Strength of recommendation (SOR)
A Good-quality patient-oriented evidence
B Inconsistent or limited-quality patient-oriented evidence
C Consensus, usual practice, opinion, disease-oriented evidence, case series
Monomicrobial infection, also referred to as type II, is often due to group A streptococcus, S aureus, vibrio spp, Aeromonas hyrophilio, or an anaerobic streptococci like peptostreptococcus spp. Typically monomicrobial infections, which account for 20% to 30% of cases of necrotizing fasciitis, are community acquired.5,26,29,30
Clinical presentation. In the early stages of disease, patients commonly complain of flu-like symptoms and extreme pain that is out of proportion to findings on the exam. Additional warning signs include fevers and other symptoms of toxicity such as tachycardia, hypotension, nausea, vomiting, and diarrhea. Later in the course, symptoms may localize to the affected area and include erythema, tense swelling, development of blisters or bullae, blackish blue discoloration of the skin, severe pain, and loss of sensation. In some cases involving gas-forming bacteria, tissue crepitus may be noted on exam.5,27-31
Rely on clinical judgment to hasten surgical intervention. Laboratory or imaging findings may augment clinical judgment. But if you suspect necrotizing fasciitis, obtaining blood tests and imaging should not delay surgery. Blood tests that may aid in the diagnosis of necrotizing fasciitis include a complete blood count with differential; coagulation studies; a comprehensive metabolic panel; assays of lactate, C-reactive protein (CRP), and creatinine kinase; and blood cultures. Most often, patients with necrotizing fasciitis will have leukocytosis or leukopenia, evidence of hemolysis, thrombocytopenia, acute renal failure, and significantly elevated CRP.
On any imaging modality, indications of necrotizing fasciitis are inflammatory infiltration of the deep fascia on the affected side that is absent on the contralateral side, and the presence of subcutaneous air (which is a specific but rare finding). Imaging modalities may include CT or magnetic resonance imaging. A definitive diagnosis can only be made with surgical exploration of the involved area. Definitive microbiologic diagnosis will require culture of organisms from affected tissue or blood.5,26,30,31
First address any hemodynamic instability (hypotension is frequently encountered), followed by urgent surgical exploration, debridement of the wound, and antimicrobial therapy. Antibiotic treatment should align with probable pathogens and treatment should be continued until repeated surgical debridement is no longer necessary, clinical improvement is evident, and 48 to 72 hours have passed since defervescence. A reasonable initial empiric regimen in adults would include an agent that is effective against group A streptococcus, gram-negative pathogens, and anaerobes, such as a carbapenem or a beta-lactam-beta-lactamase inhibitor such as piperacillin-tazobactam. Additionally, include an agent that targets MRSA, such as vancomycin, linezolid, or clindamycin.5
CORRESPONDENCE
Karl T. Clebak, MD, Department of Family and Community Medicine Residency Program, Penn State Health M.S. Hershey Medical Center, 500 University Drive, H154/C1613, Hershey, PA 17033; kclebak@pennstatehealth.psu.edu
